Abrupt sea level rise seen 15,000 years ago could happen again

London, Jan 6 (IANS) Global warming is replicating conditions that triggered an abrupt sea level rise of several meters in the ocean around Antarctica some 15,000 years ago, warns a study.

"The changes that are currently taking place in a disturbing manner resemble those 14,700 years ago," said one of the researchers Michael Weber from University of Bonn in Germany.

At that time, changes in atmospheric-oceanic circulation led to a stratification in the ocean with a cold layer at the surface and a warm layer below.

Under such conditions, ice sheets melt more strongly than when the surrounding ocean is thoroughly mixed.

This is exactly what is presently happening around the Antarctic, said the study published in the journal Scientific Reports.

"The reason for the layering is that global warming in parts of Antarctica is causing land based ice to melt, adding massive amounts of freshwater to the ocean surface," Chris Fogwill from the Climate Change Research Center in Sydney explained.

"At the same time as the surface is cooling, the deeper ocean is warming, which has already accelerated the decline of glaciers in the Amundsen Sea Embayment (in West Antarctic ice sheet)," Fogwill added.

To investigate the climate changes of the past, the scientists studied the frozen "climate archive" - drill cores from the Antarctic ice sheet.

"The largest melt occurred 14,700 years ago. During this time the Antarctic contributed to a sea level rise of at least three meters within a few centuries," Weber noted.

The research team used isotopic analyses of ice cores from the Weddell Sea region -- southernmost tip of the Atlantic Ocean - which now flows into the ocean about a quarter of the Antarctic melt.

Through a combination of ice sheet and climate modelling, the isotopic data showed that the waters around the Antarctic were heavily layered at the time of the melting events, so that the ice sheets melted at a faster rate.

"The big question is whether the ice sheet will react to these changing ocean conditions as rapidly as it did 14,700 years ago," co-author Nick Golledge from Antarctic Research Centre in Wellington, New Zealand, said.